Breathability measurement refers to a fabric's ability to allow moisture vapor to pass through, indicating how comfortable it will be during wear. The RET (Resistance to Evaporative Heat Transfer) value is commonly used; lower RET values (0-6) indicate very high breathability, while higher values (above 20) mean poor breathability.
The second way that breathability can be measured is moisture vapour transmission rate (MVTR), given in milligrams per hour (mg/h), showing how much moisture can pass through in a set time frame. Higher MVTR values indicate better breathability, ensuring comfort by reducing moisture buildup.